The present invention relates to the production of microstructures and/or microparts, and particularly to a system for developing a polymeric mold used for the production of microparts. More particularly, the present invention relates to an apparatus for producing precise, high aspect ratio polymer molds which may be adapted for fabricating micro-scale, metal, polymer, or ceramic parts using the so-called LIGA process.
LIGA, is an acronym derived from the German words for Lithography, Electroforming, and Molding. The LIGA process is being evaluated worldwide as a method to produce microstructures and/or microparts from engineering materials.
The LIGA process was pioneered in the early 1980s as a method to produce precise, high aspect ratio microstructures from engineering materials, such as various metals, polymers, and ceramics. See E. W. Becker, et al., Microelectronic Engr. 4 (1986) 35; and W. Ehrfeld, et al., KFK-Nachrichten 10(4) (1987) 167.
In the general LIGA process x-ray radiation from a synchrotron source passes through, and is patterned by, a specially designed mask to produce deep exposures in a x-ray resist, typically polymethylmethacrylate (PMMA), with precise lateral dimensions. The PMMA, after exposure, is placed in a chemical developer to remove the exposed material and produce thereby a polymeric mold. This mold is most commonly used as an electroplating template to produce metal microparts or a metal master mold. If a metal master mold is made, it can be used to produce cost-effective replicates in other materials, primarily polymers. Finally, the process can be used also to directly produce PMMA microstructures and/or microparts.
One of the appeals of LIGA as a fabrication methodology is the ability to produce precise, micro-scale parts with high aspect ratios made from traditional metallic materials. Applications such as motors, spinnerets, and switches have been explored using metal microparts fabrication from LIGA. Over the past few years there has been a growing interest in plastic parts for applications such as spectrometers, microanalytical instrumentation, and medical applications. Also emerging is an interest in ceramic materials in LIGA fabricated structures. Ceramic materials allow improved magnetic properties, piezoelectric properties, and application at higher temperatures.
In order to produce metal, plastic, or ceramic LIGA parts, it is necessary to have the appropriate equipment, systems, and processes in order to conduct synchrotron exposures and subsequent development of the exposed PMMA to produce the required polymer mold. The present invention involves an apparatus for practicing the photoresist development step of the LIGA process. In particular, the present invention is drawn to a photoresist developer system comprising a group of developer tanks; appropriate developer solutions, high frequency solution agitation, continuous solution circulation and filtration, and close temperature control of the tank contents.